The present invention refers generally to an electromotive drive mechanism for a piece of furniture, and in particular to an electromotive drive mechanism of a type having a gearmotor in driving connection with a gearing having an output member for rotating an adjusting spindle and thereby moving a nut, disposed on the spindle, in longitudinal direction of the spindle.
Drives for furniture are utilized in a variety of application, e.g. for adjusting swingable parts of a slat frame bed for hospital beds, for treatment chairs, TV chairs or similar pieces of furniture. The furniture drive can be configured as single drive with one gearmotor and one adjusting spindle, or as twin drive with two gearmotors and two adjusting spindles. Conventionally, the gearing positioned between the gearmotor and the spindle is designed as worm drive, with the worm being mounted on the driven pin of the gearmotor for reducing the relatively great speed of the gearmotor, and with the wormgear being mounted on a shaft oriented at a right angle thereto and linked to the adjusting spindle. This type of electromotive drive is applicable only for smallest outputs with a power of a few 100 watts. The speed of the adjusting spindle should be relative small to enable a slow adjustment of the piece of furniture.
There is a desire to provide drives of this type of compact design to fit the limited space available in the piece of furniture for which these drive are used. While compact designs for furniture drives have been proposed, their dimensions are still too bulky. Moreover, efforts are made to keep the power being drawn as small as possible in order to reduce the energy consumption. This objective is however difficult to reconcile with the need to provide the furniture drive with a self-locking gear unit because the efficiency of conventional self-locking gear units is in the range of 0.5 so that the energy loss is respectively high.